Effect of Soil Organic Matter Removal on Phosphorus Sorption in Some Calcareous Soils of East Azerbaijan Province

This study was carried out to obtain soil organic matter (SOM) influence on phosphorous (P) sorption in the 12 calcareous soil samples. SOM was removed with sodium hypochlorite (NaOCl) solution (pH=8).Soils were brought into equilibrium with varying solution concentrations of P, and the amounts removed from solution were used to check the fit to three adsorption isotherms, namely, Freundlich, two- surface Langmuir and Dubinin- Radushkevich. Results showed that the amount of P sorption after SOM removal was increased and fits of adsorption equations showed that single-surface Langmuir equation did not describe P sorption in the soils, but a two-surface Langmuir, Freundlich and Dubinin-Radushkevich equations showed statistically significant (P